The landscape is effectively preserved over geological timescales.
Beneath the relentless stillness of the Atacama Desert, time has been accumulating in stone for far longer than science once imagined. Researchers at the University of Cologne, using rare isotopes born from cosmic rays striking ancient rock, have determined that the desert's hyperarid core has been locked in extreme dryness for roughly 45 million years — not the 10 to 20 million previously assumed. The cause was not the Andes or the cold Humboldt Current, as long believed, but a global cooling that preceded them both, with those forces arriving later only to deepen what was already written into the land. In revising this timeline, science gains not merely a corrected date, but a vastly longer window into how life endures at the outermost edges of what water — or its absence — will allow.
- The Atacama's hyperarid core has been extreme for 45 million years, shattering the previous estimate by roughly 25 million years and forcing a fundamental rethinking of how deserts form.
- Scientists recorded the highest concentrations of the isotope 21Ne ever measured, a testament to a landscape so dry that rocks have sat undisturbed, accumulating cosmic-ray signatures, for tens of millions of years.
- The traditional culprits — Andes uplift and the Humboldt Current — are now understood as amplifiers, not originators; the true trigger was global climate cooling following the Early Eocene warm period 50 million years ago.
- The corrected timeline transforms the Atacama into a 45-million-year natural laboratory, offering scientists a far deeper record for studying how life adapts, colonizes, and evolves under near-total water scarcity.
Geologists have fundamentally redrawn the origin story of one of Earth's most inhospitable places. The Atacama Desert's hyperarid core — receiving less than 2 millimeters of rain each year — was long thought to have reached its extreme dryness between 10 and 20 million years ago. A new study published in Nature Communications by researchers at the University of Cologne, working alongside colleagues in Glasgow and Frankfurt, now places that threshold at roughly 45 million years ago.
The team analyzed 135 rock samples using cosmogenic nuclide exposure dating, measuring rare isotopes — primarily 21Ne — that form when cosmic rays strike minerals at Earth's surface. The concentrations they recorded were the highest ever reported, reflecting a landscape so stable and so dry that rocks have remained essentially undisturbed for tens of millions of years. In wetter climates, erosion constantly reshapes the land; in the Atacama's hyperarid core, the surface is frozen in geological time.
The new timeline traces the desert's extreme dryness back to the Mid-to-Late Eocene, following a period of global climate cooling after the Early Eocene Climate Optimum — a warm interval around 50 million years ago. That cooling reduced moisture across the region, initiating a slow, relentless drying that has persisted ever since. The Andes uplift and the cold Humboldt Current, long credited as the desert's creators, are now understood to have intensified conditions that were already in place rather than caused them.
The implications reach well beyond geology. The Atacama serves as a natural laboratory for studying life at the absolute limits of habitability, and knowing that hyperaridity has persisted for 45 million years — not 10 to 20 — gives researchers a far longer record to examine how organisms adapt, colonize, and survive under extreme water scarcity. The study, part of the University of Cologne's Collaborative Research Centre 1211, sets a new benchmark for understanding how landscapes stabilize and climates evolve across deep time.
Geologists have pushed back the clock on one of Earth's most inhospitable places. The Atacama Desert's hyperarid core—the driest part of an already brutally dry region—did not become extreme just 10 to 20 million years ago, as scientists long believed. Instead, it has been locked in extreme aridity for roughly 45 million years, a finding that rewrites the timeline of desert formation and forces a reconsideration of how such unforgiving landscapes take shape.
The discovery comes from a study published in Nature Communications by researchers at the University of Cologne, working with colleagues from the Scottish Universities Environmental Research Centre in Glasgow and Goethe University Frankfurt. The team analyzed 135 rock samples from the Atacama using cosmogenic nuclide exposure dating, a technique that measures rare isotopes created when cosmic rays strike minerals at Earth's surface. By measuring concentrations of the isotope 21Ne—and in some cases 10Be—the researchers could determine how long rocks have been sitting exposed on the ground without being disturbed by erosion or weathering. The results were striking: the team recorded the highest concentrations of 21Ne ever reported, indicating that surface rocks in the Atacama have remained largely undisturbed for tens of millions of years.
What makes this possible is the desert's extreme dryness. The hyperarid core receives less than 2 millimeters of rain annually. In temperate regions, precipitation drives constant erosion and landscape reshaping. Here, the landscape is essentially frozen in time. Rocks sit where they fell, accumulating cosmic-ray-induced isotopes year after year, century after century, million after million. The data tells a story written in stone: this place has been dry for an extraordinarily long time.
The timeline now extends back to the Mid-to-Late Eocene epoch, shortly after a period of global climate cooling that followed the Early Eocene Climate Optimum, a warm spell roughly 50 million years ago. That cooling event appears to have reduced moisture availability across the region, transforming what was already semi-arid into something far more extreme. The shift was not sudden or catastrophic—it was the beginning of a slow, relentless drying that would persist for the next 45 million years.
This reframing changes how scientists understand what created the Atacama. The traditional explanation pointed to two major factors: the uplift of the Andes Mountains and the influence of the cold Humboldt Current, which flows along South America's Pacific coast. Both are real and important. But the new evidence suggests they did not initiate hyperaridity. Instead, they intensified and expanded conditions that were already in place. The desert's extreme dryness was born from global climate change; the mountains and ocean current locked it in and made it worse.
The implications extend beyond desert geology. The Atacama is a natural laboratory for understanding life at the absolute limits of habitability. Water defines whether a planet can support life, yet vast regions of Earth exist under severe water scarcity. In such places, both biological activity and surface processes are constrained in ways scientists are still working to understand. By establishing that the Atacama has been hyperarid for 45 million years—not 10 to 20 million—researchers now have a much longer temporal window to study how life adapts, evolves, and persists under extreme water limitation. Rare and brief increases in moisture during that span may have left marks on the landscape and influenced which organisms could colonize and survive. Understanding those connections requires knowing the full climate history, which this study now provides.
The work is part of a larger research initiative at the University of Cologne called the Collaborative Research Centre 1211, which investigates how life and Earth surface processes co-evolve under extreme water scarcity. The extended timeline offers crucial context for identifying thresholds for biological colonization, understanding evolutionary adaptation to changing climates, and mapping the interplay between geological processes and biodiversity in Earth's most extreme environments. With its unprecedented dataset and record-setting isotope measurements, the study establishes a new benchmark for investigating how landscapes remain stable and climates evolve over tens of millions of years.
Citações Notáveis
This makes it one of the longest continuously dry regions on Earth and forces us to reconsider how and when such extreme environments develop.— Dr. Benedikt Ritter-Prinz, University of Cologne
In the Atacama's hyperarid core, with less than 2 millimeters of annual rainfall, surface processes are extraordinarily slow and the landscape is effectively preserved over geological timescales.— Prof. Tibor Dunai, University of Cologne
A Conversa do Hearth Outra perspectiva sobre a história
Why does it matter that the Atacama became hyperarid 45 million years ago instead of 10 to 20 million years ago? That's a long time either way.
The difference is the length of the experiment. If you're trying to understand how life adapts to extreme dryness, you need to know how long that dryness has persisted. Forty-five million years is three times longer than the old estimate. That's three times as many generations of organisms trying to survive, three times as many climate fluctuations to respond to.
So the rocks themselves are the evidence? They're just sitting there, accumulating isotopes?
Exactly. In a wet place, rain and wind constantly break down rocks, move sediment around, erase the record. In the Atacama, nothing happens. A rock lands on the ground and stays there for millions of years, collecting cosmic-ray signatures like a clock that never stops.
And this changes what we thought caused the desert?
It does. We used to think the Andes Mountains and the cold ocean current created the hyperaridity. Now we see those were reinforcements, not the origin. The real trigger was global cooling 45 million years ago, which dried out the region. The mountains and the current made it worse and kept it that way.
What does this tell us about life in the Atacama?
That's the open question. If organisms have been adapting to extreme dryness for 45 million years, not 10 to 20, then the evolutionary pressures are much deeper, much more refined. We need to understand what that means for how life persists at the edge of habitability.
Is there anything alive there now?
There is, but barely. Microbes, some hardy plants, insects. The point is to understand how they got there and how they've changed over that immense span of time.